﻿////-----------------------------------------------------------------------
//// <copyright company="www.3WayWebdesign.de">
//// Permission is hereby granted, free of charge, to any person obtaining
//// a copy of this software and associated documentation files (the
//// "Software"), to deal in the Software without restriction, including
//// without limitation the rights to use, copy, modify, merge, publish,
//// distribute, sublicense, and/or sell copies of the Software, and to
//// permit persons to whom the Software is furnished to do so, subject to
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////
//// The above copyright notice and this permission notice shall be
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//// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
//// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
//// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
//// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
//// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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//// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//// </copyright>
////
//// <author>Michael Morbach</author>
//// <email>Michael@3waywebdesign.de</email>
//// <web>http://www.3waywebdesign.de</web>
////-----------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using GalaSoft.MvvmLight;

namespace Tww.MAF.MAFEngine.Navigator
{
    public class NavigationJournal : ViewModelBase, INavigationJournal
    {
        #region  - Felder (privat) -

        private INavigationJournalEntry currentEntry;

        #endregion

        public NavigationJournal()
        {
            this.BackStack = new Stack<INavigationJournalEntry>();
            this.ForwardStack = new Stack<INavigationJournalEntry>();
        }

        #region  - INavigationJournal Members -

        /// <summary>
        /// Gets a value that indicates whether there is at least one entry in the back navigation history.
        /// </summary>
        /// <value>
        ///   <c>true</c> if the journal can go back; otherwise, <c>false</c>.
        /// </value>
        public bool CanGoBack
        {
            get { return BackStack.Count > 0; }
        }

        /// <summary>
        /// Gets a value that indicates whether there is at least one entry in the forward navigation history.
        /// </summary>
        /// <value>
        /// <c>true</c> if this instance can go forward; otherwise, <c>false</c>.
        /// </value>
        public bool CanGoForward
        {
            get { return ForwardStack.Count > 0; }
        }

        public INavigationJournalEntry CurrentEntry
        {
            get { return this.currentEntry; }
            set
            {
                this.currentEntry = value;
                RaisePropertyChanged(() => CurrentEntry);
            }
        }

        /// <summary>
        /// Navigates to the most recent entry in the back navigation history, or does nothing if no entry exists in back navigation.
        /// </summary>
        public void GoBack()
        {
            if (CanGoBack)
            {
                INavigationJournalEntry destination = BackStack.Peek();
                CurrentEntry.NavigationLocation.RequestNavigate(destination.Uri,
                    result =>
                    {
                        if (result.Result.GetValueOrDefault())
                        {
                            if (CurrentEntry != null)
                            {
                                ForwardStack.Push(CurrentEntry);
                            }

                            BackStack.Pop();
                            CurrentEntry = destination;
                        }
                    });
            }
        }

        /// <summary>
        /// Navigates to the most recent entry in the forward navigation history, or does nothing if no entry exists in forward navigation.
        /// </summary>
        public void GoForward()
        {
            if (CanGoForward)
            {
                INavigationJournalEntry destination = ForwardStack.Peek();
                CurrentEntry.NavigationLocation.RequestNavigate(destination.Uri,
                    result =>
                    {
                        if (result.Result.GetValueOrDefault())
                        {
                            if (CurrentEntry != null)
                            {
                                BackStack.Push(CurrentEntry);
                            }

                            ForwardStack.Pop();
                            CurrentEntry = destination;
                        }
                    });
            }
        }

        /// <summary>
        /// Navigates directly to the specified entry
        /// </summary>
        /// <param name="journalEntry">The entry to record</param>
        /// <exception cref="System.NotImplementedException"></exception>
        public void GoTo(INavigationJournalEntry journalEntry)
        {
            throw new NotImplementedException();
        }

        /// <summary>
        /// Records the navigation to the entry..
        /// </summary>
        /// <param name="journalEntry">The entry to record.</param>
        public void RecordNavigation(INavigationJournalEntry journalEntry)
        {
            if (CurrentEntry != null)
            {
                BackStack.Push(CurrentEntry);
            }

            ForwardStack.Clear();
            CurrentEntry = journalEntry;
        }

        /// <summary>
        /// Clears the journal of current, back, and forward navigation histories.
        /// </summary>
        public void Clear()
        {
            CurrentEntry = null;
            BackStack.Clear();
            ForwardStack.Clear();
        }


        public event NotifyCollectionChangedEventHandler CollectionChanged;

        /// <summary>
        /// Gets the back stack.
        /// </summary>
        /// <value>
        /// The back stack.
        /// </value>
        public Stack<INavigationJournalEntry> BackStack { get; private set; }

        /// <summary>
        /// Gets the forward stack.
        /// </summary>
        /// <value>
        /// The forward stack.
        /// </value>
        public Stack<INavigationJournalEntry> ForwardStack { get; private set; }

        #endregion
    }
}